Aspects of endocannabinoid signaling in periimplantation biology

Physiological roles of endocannabinoids, a group of endogenously produced cannabinoid-like lipid molecules that activate G protein-coupled cannabinoid receptors, are being increasingly appreciated in female reproduction. Adverse effects of cannabinoids on female fertility have been suspected for decades; however, underlying molecular and genetic bases by which they exert these effects were not clearly understood. The discovery of cannabinoid receptors (CB1 and CB2), endocannabinoid ligands (anandamide and 2-acylglycerol) as well as their key synthetic and hydrolytic pathways has helped to better understand the roles of cannabinoid/endocannabinoid signaling in preimplantation embryo development, oviductal embryo transport, embryo implantation and postimplantation embryonic growth. This review focuses on various aspects of the endocannabinoid system in female fertility based on studies that used knockout mouse models. The information generated from studies in mice is likely to shed deeper insight into fertility regulation in women.